Filters for shielding electrical connectors from electromagnetic interference (EMI) are known in the art. Various filter configurations have been utilized for this purpose, including those composed of only a capacitor (C filters) and those which further include inductive and resistive elements (LC, CLC and CLCR filters). Generally, filters which are equipped with an inductor between a pair of capacitors (CLC or pi filters) offer the most effective shielding from EMI.
In the automotive industry, capacitor filters have been used to provide EMI shielding for electrical connectors, particularly those connectors used for engine control circuitry. Prior art filters which have been employed for this purpose have generally consisted of surface mounted ceramic chip capacitors which are mounted on a polyimide substrate. For optimal filtration in which a pi filter is used, each pin of the connector must be equipped with two chip capacitors, necessitating four capacitor solder joints. For a 160 pin connector of a type used in engine control, the above structure requires the use of 320 chip capacitors, necessitating 640 solder joints. Consequently, such prior art pi filters are complicated and costly to manufacture, and their reliability is dependent on the reliability of a large number of capacitors and their solder connections. Scrappage also tends to be higher as a result of the number of solder joints required with this type of filter structure.
Accordingly, it would be desirable to provide a filter for electrical connectors whose structure and manufacture is less complicated than that of filters composed of soldered chip capacitors. Such a filter would preferably offer design flexibility to allow the filter to be configured as a C, LC, CLC or CLCR filter, so as to be readily configurable to allow its capacitance to be tailored to filter certain frequencies, and also structured to promote the ease with which the filter is assembled with a connector.